Example2.cs

public double ShipmentDistance(ExternalShipment shipment)
{
    var miles = shipment.Stops.Sum(x => x.Miles);
    return MilesToKilometers(miles);
}

public double TollDistance(ExternalShipment shipment)
{
    var miles = shipment.Stops
        .Where(x => x.HasTolls)
        .Sum(x => x.Miles);
    return MilesToKilometers(miles);
}

private double MilesToKilometers(double miles)
{
    return miles * 1.60934;
}